Gestion des ressources naturelles

La gestion des ressources naturelles est une gestion qui permet à ces ressources de se renouveler et d'être conservées de manière pérenne, sans être menacées par la surexploitation. La surexploitation a été identifiée dès le / comme cause de stagnation voire de recul économique par David Ricardo et Thomas Malthus. Cette gestion durable est une condition et un enjeu de survie pour l'humanité et de nombreuses autres espèces qui partagent la biosphère avec elle. Elle est un des éléments du développement soutenable. En économie, le principe de la rente d'Hotelling (ou « rente de rareté ») postule qu'une rente est rendue possible par la quantité limitée de ressources non renouvelables ; situation qui peut conduire à la surexploitation d'une ressource fut elle vitale (ex : surpêche). Au-delà d'un certain seuil (de pression, qui est aussi le seuil de surexploitation), une ressource a priori renouvelable (ex : forêt, ressource halieutique ou cynégétique) peut devenir épuisable ; la gestion

Towards Solar Decathlon: Concepts for a Sustainable Urban Water Management in a new eco-district

Gianluca Antonio Paglia

Water is rarely considered to be a crucial aspect in sustainable housing. In fact, water sustainability in eco-districts and in ecological architecture is frequently limited to recycling and reuse solutions. Why less water? What could explain the choice of an installation, of a specific strategy or of a criterion trying to decrease water needs? Terms as ecological footprint or sustainability are becoming more and more used, however, how can sustainability be measured? What does sustainable water mean? What are the parameters that quantify the ecological footprint of a water management system? Within this project, some possible concepts of optimization and valorization of sustainable urban water system have been defined and explored. Numerous studies about water management, water distribution, sanitary technologies, recycling, etc. have already been done. Nevertheless, it is less common to identify the reasons that are able to justify a reduced consumption of water. Eco-district labels propose several solutions for sustainable water, however they are limited by scale or simply focused on one stage of the water cycle. The aim of this project is then to consider water from a larger point of view: through a Life Cycle Analysis approach, needs and properties of different urban water management systems are compared and evaluated. The scale considered for such reflections is effectively a central parameter; in this case, hypothesis will be applied to collective habitations inserted in a district and part of a specific urban context: the city of Fribourg. The urban environment has particular features in relation to surrounding rural areas: energy exchanges, hydrology characteristics and limited ecosystems. The relationship between the use of natural resources and urban development is becoming more and more important; the purpose of this thesis is then to define a methodology able to suggest a sustainable use of water through environmental, political and economic issues. A real urban case study with its current water management system defines what has to be analyzed and allows evaluating the limits and the possible enhancements of such system. Thus, in order to have an idea about the potential of sustainable water management solutions, an ambitious analysis of energy related to water uses and disposals is created and is used to show the reasons for change in a real model as the city of Fribourg. A comparison between two extreme scenarios of Fribourg’s selected zones is finally developed, discussed and implied in the conclusions through specific actions and facts. The results show that a high potential of improvements exist. Using them to elaborate new strategies in collaboration with the several stakeholders contacted may contribute to achieve many of today’s objectives for a sustainable urban water management. The best scenario, chosen with a new concept of eco-label, summarizes and concludes the analysis.

2015

Méthodologie multicritère d'aide à la décision pour le renouvellement urbain à l'échelle du quartier

Maria Gracia Riera Perez

The present work develops a new methodology for assessing urban renewal scenarios at the neighborhood scale. Entitled URBIUS, this methodology seeks to meet the needs of municipalities in terms of planning for the development of their urban built fabric. It is now widely recognized that the urban population growth, along with the increase in the use of private vehicles, has led to a generalized urban sprawl. This land use is not sustainable in environmental, social and economic terms. Because most European cities are in this situation, it appears necessary to bring new developments within the urban built fabric, in order to raise their density. However, to rely on densification alone is not sufficient in order to move towards a more sustainable urban environment and to attract new residents looking for quality living spaces. Therefore, the transformation of the city requires a holistic vision, integrating different objectives. In this perspective, the neighborhood scale has been identified as an operational scale which integrates both the specific objectives of stakeholders taking part in the making of the city and the broader objectives of the city itself. In this context, this work seeks to contribute to the inward development of the cities in a qualitative way, by providing URBIUS, a new methodology for assessing the sustainability of urban renewal strategies at the neighborhood level. Prior to the creation of this methodology, an operational definition of sustainable neighborhoods has been developed. This one includes six goals: to ensure the feasibility of the urban renewal strategy, to provide housing to all residents, to balance the supply of jobs and housing, to save energy resources, to upgrade the local natural resources and to promote the balance between density and urban quality. Hence, the methodology is structured following these six goals and declines them in criteria and indicators for the purpose of the assessment. For each indicator, both quantitative and qualitative, assessment thresholds are set: a limit value and a target value. These thresholds are used to assess the strategies positively if the value is better than the target value, negatively if it is worse than the limit value, and uncertain for values lying between the limit value and the target value. However, in order to adjust the assessment to the specific potential of a neighborhood, an adaptation technique has been developed based on a dynamic approach. The assessment thresholds are adapted depending on the evaluation of the existing state of the neighborhood and on its underlying trend, that is to say the assessment of the neighborhood at a given time whereas no special action is planned. Finally, the new methodology is tested on four neighborhoods taken as case studies. The chosen neighborhoods have all a good quality public transportation system, with potential for densification and capacity to provide quality living space. They are located in the canton of Vaud, Switzerland: Lausanne, Prilly, Echallens and Yverdon-les-Bains. This work highlights the potential of urban renewal strategies at the neighborhood scale in the process of the transformation of the city towards greater sustainability and the contribution of sustainability assessment methodologies. In this sense, URBIUS is a relevant methodology to assist and foster sustainable urban renewal. Now it is up to the key stakeholders to undertake such efforts in urban renewal in a concerted and sustained effort.

EPFL2016

Electrochemical Reduction of CO2 Catalyzed by Metal Oxides

Yeonji Oh

A rapidly growing population and industrialization have caused the exploitation of natural resources in keeping with fossil fuels shortage. Due to the combustion of fossil fuels, the concentration of CO2 in the earth's atmosphere, which is a potent greenhouse gas, has been increasing dramatically and contributes to the current climate change. Meanwhile, CO2 can be considered as an abundant and inexpensive carbon feedstock, especially if carbon sequestration is required for future fossil fuel-based power stations. Electrochemical reduction of CO2 to form useful chemicals or fuels is a potentially efficient method of CO2 utilization and recycling. The advantage of the electrochemical CO2 reduction is that natural renewable sources, like solar power, wind power, hydropower or nuclear power can supply electric power for CO2 conversion. Various products, such as carbon monoxide, oxalic acid, formic acid, alcohols and hydrocarbons have been reduced from CO2 First in chapter 1, the general remarks about electrochemical reduction of CO2, especially on metal electrodes are introduced. It also includes the introduction of photoelectochemical CO2 reduction and literature review study about electrocatalytic CO2 reduction with organic molecules as mediators and catalysts. In chapter 2, our interest in Mo-based electrocatalysts led us to study the activity of MoO2 for CO2 reduction. MoO2 microparticles indeed act as an active catalyst for the electrochemical reduction of CO2 in organic solvents such as acetonitrile (MeCN) and dimethylformamide (DMF). In the context of this study, it was found that the CO2 reduction activity is much higher at -20 oC than at RT, and it can be promoted by a small amount of water. The selectivity of CO2 reduction depends on the temperature, overpotential and water concentration. Chapter 3 describes the electrochemical reduction of CO2, improved and modified by using imidazolium ionic liquids (ILs) as an electrolyte in organic solvent with MoO2/Pb electrode. The important role of ILs in changing the pathway of the reduction was observed. Particularly, the use of imidazolium ILs instead of tetraalkylammonium salt as an electrolyte altered the product from oxalate to CO. Besides, the overpotential of the CO2 reduction was shifted to the less negative potentials compared to previous work, and the current density as well increased. At a low water concentration, the catalytic activity was promoted and the total Faradaic efficiency (FE) was up to 100% with more than 60% of CO formation. Furthermore, imidazolium ILs together with our MoO2/Pb electrode lowered the overpotential of CO2 reduction by about 40 mV. In addition to the high selectivity for CO formation, the imidazolium ILs can perform a role as co-catalyst for lowering the CO2 reduction potential. Finally, chapter 4 shows the possibility of photoelectrochemical CO2 reduction to extend our research with various catalysts. In this work, we could derive a photoelectrochemical method to deposit Sn/SnOx catalyst on the surface protected cuprous oxide (Cu2O) photocathodes. The deposition of Sn/SnOx catalyst was optimized on the photocathode and it exhibited reliable CO2 reduction activity in a mild aqueous condition. Sn/SnOx-Cu2O photocathode showed the onset potential of the photocurrent at +0.1 V vs. RHE, which is very promising result. At a constant potential electrolysis of -0.1 V vs. RHE, a FE of 50% for formate formation was obtained and the total FE was around 86%.

EPFL2015